1. Field of the Invention
This invention relates to an exerciser, such as a back extension machine or a leg extension machine, and more particularly to an exerciser which includes a light emitting element that generates a light beam for correcting the posture of the user of the exerciser.
2. Description of the Related Art
Referring to FIG. 1, a conventional back extension machine is shown to include a supporting frame unit 1, a swing rod 2 disposed pivotally on the frame unit 1, and a counterweight unit 3. The supporting frame unit 1 has a brace 101 that supports a seat 102 fixedly on an upper end thereof. The seat 102 is disposed below the swing rod 2. Two foot plates 103 are disposed fixedly on a lower end portion of the brace 101. The swing rod 2 is provided with a fixed back cushion 201 that is disposed above the seat 102. A pull rope 202 extends around a pulley 203, and is fastened to the swing rod 2 at one end, and to the counterweight unit 3 at another end.
Referring to FIGS. 2 and 3, the user sits on the seat 102 in such a manner that his feet rest on the foot plates 103. To exercise the muscles of the user""s back, the back of the user turns the back cushion 201 rearwardly so as to rotate the swing rod 2 synchronously with the back of the user, thereby pulling the counterweight unit 3 upwardly. It should be noted that if the rotating axes of both the swing rod 2 and the back joint of the user are improperly coordinated, the swinging movement of the swing rod 2 will hurt the back muscles and the back joint of the user.
Referring to FIG. 4, a conventional leg extension machine is shown to include a supporting frame unit 4, a swing rod 5 disposed pivotally on the supporting frame unit 4, and a counterweight unit 6. The frame unit 4 is provided with a fixed seat 401, a fixed backrest 402 and a fixed handle unit 403. The swing rod 5 is provided with a shank cushion 501 that is located below the seat 401. A pull rope 502 extends around a pulley 503, and is fastened to the swing rod 5 at one end, and to the counterweight unit 6 at another end.
Referring to FIGS. 5 and 6, the user sits on the seat 401, and grasps the handle unit 403. The back of the user abuts against the backrest 402. To exercise the muscles of the user""s legs, the calves of the user turn the shank cushion 510 forwardly and upwardly so as to rotate the swing rod 5 synchronously with the calves of the user, thereby pulling the counterweight unit 6 upwardly. It should be noted that if the rotating axes of both the swing rod 5 and the knee joint of the user are improperly coordinated, the swinging movement of the swing rod 5 will hurt the leg muscles and the knee joint of the user.
To help correct the posture of the user with respect to the swing rod 5, a mark is provided to indicate the correct position of the joint of the user on the exerciser. For example, referring to FIGS. 7 and 8, each of a pair of improved back and leg extension machines includes a colored cap 801, 801xe2x80x2, which covers a pivot that connects a swing rod 8, 8xe2x80x2 rotatably to a supporting frame unit 7, 7xe2x80x2. The body of the user can move on the frame unit 7, 7xe2x80x2 by adjusting the position of at least one element, such as a seat, a shank cushion, a back cushion or a backrest, relative to the frame unit 7, 7xe2x80x2 so as to align his joint with the cap 801, 801xe2x80x2. However, because the cap 801, 801xe2x80x2 is spaced apart from the body of the user, it is difficult to align the joint of the user accurately with the cap 801, 801xe2x80x2.
An object of this invention is to provide an exerciser which includes a light emitting element that generates a light beam for indicating a correct position of one joint of the user on the exerciser.
According to this invention, an exerciser includes a seat attached to a supporting frame unit, and a swing rod disposed pivotally on the supporting frame unit and adapted to be swung by a portion of a human body so as to rotate synchronously with the portion of the human body about a rotating axis. A light emitting element is mounted on an assembly of the supporting frame unit and the swing rod so as to generate a light beam that extends along the rotating axis. When the human body sits on the seat, the portion of the human body can move on the supporting frame unit so as to align the light beam accurately with the rotating axis of one joint of the human body, about which the portion of the human body rotates.